Project Number: JYP-1102 A Chlorination System for the Scum Manhole at the Sturbridge Wastewater Treatment Plant A Major Qualifying Project Proposal submitted to the Faculty of WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Bachelor of Science By Nicole D’Angelo Emily Dudley Kimberly Woodward Date: February 24, 2012 Approved: Professor Jeanine Plummer, Major Advisor Professor John Bergendahl, Co-Advisor 1. Wastewater treatment 2. Nocardioform 3. Chlorination Abstract The goal of this project was to design a system for reducing nocardioform bacteria within the Sturbridge Wastewater Treatment Plant in Sturbridge, MA. Nocardioform bacteria at the plant cause foaming in the clarifier and reduce the ability to recover ballast from the foam. Foam samples from the surface of the aeration basin were chlorinated and then analyzed for settleability and cell characteristics via microscopy. A hypochlorite feed design option was chosen to inactivate and separate nocardioform bacteria within a concentrated scum manhole after aeration basin surface wasting. Recommendations for system run-time, the installation of the system, and measuring the success of the system once implemented were provided at the conclusion of this report. ii Executive Summary Nocardioform foaming in wastewater treatment plants creates hazardous working conditions and may compromise the effectiveness of downstream processes. The Sturbridge Wastewater Treatment Plant in Sturbridge, MA experiences foaming due to nocardioform bacteria in the aeration basins. Common methods to control and reduce foam include varying operating factors such as mean cell residence time and pH levels. Surface wasting and disinfection are also commonly used. Currently the plant is using a chemical defoaming agent to reduce foam, but the nocardioform bacteria still persist. During the completion of this project, the Sturbridge WWTP was undergoing an upgrade to a magnetic ballast addition system called BioMag, prior to secondary treatment. The plant operators were concerned with the amount of magnetite ballast that was being captured within the dense surface foam and ultimately wasted through the sludge handling processes. Thus, a reduction in foam could potentially result in increased magnetite recycle rates and decreased monetary losses. The goal of this project was to develop an effective nocardioform control strategy that does not compromise downstream processes and reduces or eliminates the use of chemical defoamer. Major objectives included: Weekly foam sampling to analyze characteristics of the foam; Analysis of chlorine effect on nocardioform bacteria; and, Development of an appropriate chemical dosage design necessary to inactivate nocardioform bacteria. Foam samples were collected four times from October to December 2011 from the scum manhole where surface foam was wasted. Samples were chlorinated with liquid sodium hypochlorite from 0 to 20 mg/L. The samples were analyzed under standard, fluorescence, and phase contrast microscopes to determine the effect of chlorine on the nocardioform bacteria. Samples were also analyzed for foam settleability. Microscopy and settleability tests yielded inconclusive results; therefore, a chlorine dose of 50 mg/L was based on recommendations by Tighe & Bond, Inc. A hypochlorite feed system to the scum manhole was recommended for increased foam control and magnetite recovery. The chlorination system was designed using a combination of plant water and liquid hypochlorite solution, discharged into the scum manhole via an eductor. The system would run during the time of surface wasting from the aeration basin, chlorinating the foam wasted into the scum manhole. The project includes design and operating recommendations for the chlorination system. Estimated capital costs for the chlorination system are $310, for equipment and materials. Operational costs are estimated at $82 daily and $29,816 annually based on current hypochlorite solution costs and manufacturer data. The operational cost of the defoaming chemical currently being used to reduce foam at the plan are $47 to $95 daily and $17,255 to $34,509 annually. The newly designed hypochlorite feed system should increase magnetite recovery and improve efforts to control foam. iii Acknowledgements This project team would like to thank the following individuals: Professor John Bergendahl and Professor Jeanine Plummer of Worcester Polytechnic Institute for technical recommendations as well as review of the design and report throughout the duration of the project; Professor Daniel Gibson of Worcester Polytechnic Institute for guidance and assistance with our microscopy methods; Ian Catlow of Tighe & Bond, Inc. for recommendations throughout the duration of the project as well as review of the design; Ryan Siegel of Tighe & Bond, Inc., Roy Wood, President of Great Blue Heron Management, and Gerry Ballentine of Veolia Environmental Services for assistance while on-site at the Sturbridge Wastewater Treatment Plant; and, All staff at the Sturbridge Wastewater Treatment Plant for their cooperation and assistance throughout this process. Without the contributions of these individuals, the success of this project would not have been possible. iv Capstone Design Statement The purpose of this Major Qualifying Project (MQP) was to design a hypochlorite feed system for the Sturbridge Wastewater Treatment Plant in Sturbridge, MA. The aeration basin/clarifier at the Sturbridge WWTP contains nocardioform bacteria, which, cause foaming problems atop the treatment unit. Because the Sturbridge WWTP uses BioMag technology for treatment, these bacteria are also responsible for a reduction in overall magnetite recovery throughout the system. The surface foam containing these bacteria is currently manually treated daily with a chemical de-foamer. This current treatment technique is not producing any noticeable positive results for the plant in terms of magnetite recovery and/or foam reduction. To address the bacteria problem, different treatment options were considered and evaluated. Based on research and conversations with engineers from our external project sponsor, Tighe & Bond, Inc., treatment of surface wasted foam in the scum manhole was recommended. Chlorination of the wasted foam in the scum manhole would allow for direct treatment of the nocardioform bacteria before being sent for magnetite recovery, further treatment, and eventual re-introduction into the plant. The following design considerations were addressed throughout this project: Hydraulic Conditions o Plant hydrant pressure (source water for designed system) o Flow rates throughout the system o Flow rate of foam entering and exiting the scum manhole o Eductor sizing Sturbridge WWTP Considerations o Cost of designed system o Increased magnetite recovery o Over time, reduction in the foam causing nocardioform bacteria re-introduced into the system Economic Considerations o Cost comparison between the use of the defoamer and the implementation and use of the designed system These considerations allowed our team to design a chlorination system appropriate for the Sturbridge WWTP. v Table of Contents Abstract ........................................................................................................................................... ii Executive Summary ....................................................................................................................... iii Acknowledgements ........................................................................................................................ iv Capstone Design Statement ............................................................................................................ v List of Figures .............................................................................................................................. viii List of Tables ................................................................................................................................. ix 1.0 Introduction .......................................................................................................................... 1 2.0 Background .......................................................................................................................... 2 2.1 Wastewater Treatment and Regulations ........................................................................... 2 2.1.1 Wastewater Treatment .............................................................................................. 2 2.1.2 EPA Regulations ....................................................................................................... 4 2.2 Activated Sludge Treatment ............................................................................................. 6 2.2.1 Process ...................................................................................................................... 6 2.2.2 Microorganisms in Activated Sludge ........................................................................ 7 2.2.3 Solids Separation Problems: Foaming ...................................................................... 8 2.3 Foam Causing Filamentous Bacteria................................................................................ 9 2.3.1 Foaming Problems .................................................................................................. 10 2.3.2 Common Methods to Control Filamentous Bacteria Foaming ..............................